New Titanium-based Mercury Film Electrode Voltammetric Determination Of Sulfonamides

Hg/Ti electrode was prepared by using elctrodeposition and photochemical deposition methode.Experiments were optimized by means of orthogonal test design.Under the most ideal condition, sulfadiazine(SDA) and trimethoprim(TMP) could be determined by the adsorptive stripping voltammetry and the differential pulse voltammetry based on electrochemical and photochemical deposition of Hg on Ti electrode respectively.The electrochemical reaction mechanisms of these two sulfa drugs were also discussed.It was found that a sensitive oxidation peak of sulfadiazine was obtained in B-R solution based on electrochemical deposition of Hg on Ti electrode.The peak current signal was better than it on the pure Ti electrode.The optimized condition was obtained as pH of 1.98,starting potential of 0.28V,scanning vate of 0.10V/s,alternation of sampling of 1.0s,time of Hg deposition of 8.0 min.The oxidation peak current was linearly proportional with the concentration of sulfadiazine over the range of 1.2×10^-6 to 1×10^-4 mol/L(R=0.99495) with the limit of 3.86×10^-7 mol/L.The effectiveness of present simulated samples were determined the recovery results were 93.83%～111.5%.It was found that photochemical deposition of Hg occurred at the layer of TiO₂ covered on the surface of titanium electrode under UV irradiation,the adsorption of sulfadiazine on the photochemically deposited Hg was stronger than that on the electrochemically deposited Hg,and a method for the determination of sulfadiazine was proposed by the adsorptive stripping voltammetry based on photochemical deposition of Hg on Ti electrode.The affecting factors such as pH,time of adsorption,starting potential of stripping process and scanning rate were studied.It was found that a sensitive oxidation peak of sulfadiazine was obtained at around 0.48 V in B-R solution of pH 1.89,and the oxidation peak current was linearly proportional with the concentration of sulfadiazine over the range of 1.2×10^-8 to 1×10^-6 mol/L(R=0.99715) with the limit of 4.35×10^-9 mol/L and the recovery results were 94.18%～111.2%.Sulfadiazine(SDA) and trimethoprim(TMP) could be determined simultaneously by means of differential pulse voltammetry.The using of photochemical deposition of Hg occurred at the layer of TiO₂ covered on the surface of titanium electrode and differential pulse voltammetry can improved the sencitivity with compare to two front experimentation.The limit of determination of sulfadiazine was 3.68×10^-11 mol/L and the recovery results were 96.87%～110.3%;The limit of determination of trimethoprim was 3.25×10^-11 mol/L and the recovery results was 94.18%～103.3%.Many parameters were also obtained:electron transfer number:n_SD=2,n_TMP=3;electron transfer coefficient:α_SD=0.74,α_TMP=1.03;proton transfer number:m_SD=1,m_TMP=1.